code: def unregister(fn):
      """Deprecated; see unregisterCallback
  
      Unregister a previously registered callback.
      """
      old_callbacks.remove(fn)
  
file_path: pyqtgraph/pyqtgraph/exceptionHandling.py
imports: import sys
  import threading
  import time
  import traceback
  from types import SimpleNamespace
label_desc: Use image node_id 4 for calling a global function with example usage: unregister(fn) without return types